package net;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UdpEchoServer {
    private DatagramSocket socket = null;

    //参数的端口表示我们服务器要绑定的端口
    public UdpEchoServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }

    //启动服务器
    public void Start() throws IOException {
        System.out.println("服务器启动!");
        while(true){
            //循环里面处理一次请求
            //1.读取请求并解析
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacket);
            //把这个DatagramPacket对象转成字符串方便打印
            String request = new String(requestPacket.getData(),0,requestPacket.getLength());

            //2.根据请求计算响应
            String response = process(request);

            //3.把响应写回客户端
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),response.getBytes().length,
                    requestPacket.getSocketAddress());
            socket.send(responsePacket);

            //4.打印一个日志，记录当前的情况
            System.out.printf("[%s:%d] request: %s ;response: %s\n",requestPacket.getAddress().toString(),
                    requestPacket.getPort(),request,response);
        }
    }

    public String process(String request) {
        return  request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server = new UdpEchoServer(9090);
        server.Start();
    }

}
